DE69121862T2 - Component for a honeycomb core and a plate structure with this honeycomb core - Google Patents

Description

The present invention relates to a honeycomb element and a honeycomb panel. The honeycomb panel can be formed using a single honeycomb element or by arranging a plurality of honeycomb elements.

Typically, a honeycomb core consists of a plurality of closed-ended dense cells and can be used as the core for a flat honeycomb panel. The cells are usually hexagonal or square in cross-section; when a honeycomb core or panel is used for various constructions, curved configurations are often required. A curved honeycomb core or panel is normally made by merely bending the sheet material. However, other methods of making a curved honeycomb core or panel are also known and will now be explained.

As shown in Figure 9, flexible honeycomb elements are manufactured, which consist of cells formed by curved surfaces. The honeycomb elements are then glued, soldered or welded together along a desired curvature to form a honeycomb core.

According to a second known method shown in Figure 10, a plurality of strip materials 101 are bonded together by applying an adhesive to hatched portions 102 and then formed into a laminate 103. After a hatched portion 104 is removed from the laminate 103, the laminate 103 is expanded to form a curved honeycomb core 105. The curved honeycomb core 105 is then placed between end plates 106 and 107 and bonded to produce a curved honeycomb panel.

JP-58-25531-A describes another method shown in Figures 11A to 11d. A strip material 111 is folded along fold lines 112 and 113. As shown in Figure 11A, the fold lines 112 are perpendicular to a center line CL and the fold lines 113 are oblique to the center line CL. The strip material 111 is then folded along the fold lines 112 and 113 to form a corrugated plate 116. As shown in Figures 11B and 11C, the corrugated plate 116 has inclined ridges 114 and recesses 115. As shown in Figure 11D, when the corrugated plate 116 overlaps with another corrugated plate, the ridges 114 of one corrugated plate 116 are attached to the recesses 115 of the other corrugated plate 116 by spot welding, thus forming hexagonal cells 118 and producing a curved honeycomb core 117.

The processes described above for producing curved honeycomb cores or panels are many problems. When a curved honeycomb core is produced by bending the sheet material in the first-mentioned prior art method, the honeycomb core resists the force required for bending, so that only large radii of curvature are possible. Small radii of curvature cannot be obtained using this method.

In the second prior art method shown in Figure 9, the materials of the honeycomb cores have such a special shape that positioning the materials for forming the cells is problematic when the honeycomb cores are laminated together. This significantly increases the manufacturing time. In addition, it becomes more difficult to form the desired honeycomb core because its height increases due to the required curvature.

The third prior art method shown in Figure 10 requires a large number of process steps, which increases the manufacturing time. Furthermore, the honeycomb core 105 is not adequately supported perpendicular to the defined curvature, so that the honeycomb panel produced has insufficient strength.

In the last-mentioned prior art method according to Figures 11A to 11B, it is difficult to form the selected plate 116 by folding the strip material 111 along the fold lines 112 and 113. It is also difficult to form the cells 118 having a hexagonal cross section by positioning and fixing the corrugated plates 116. Moreover, the corrugated plates 116 are bent only with a limited radius of curvature. This method is insufficient to honeycomb cores or panels with varying radii of curvature.

A honeycomb element having the features of the preamble of claim 1 is known from US-A-3 068 565, in particular from Figure 5 of this publication. Adjoining side edges of two abutting surfaces of this known honeycomb element form a comparatively wide opening. This opening is only closed when a plurality of the honeycomb elements are arranged in the manner shown in Figure 5 of this publication. In order to give a honeycomb core consisting of a plurality of the known honeycomb elements sufficient strength, the elements are soldered together at contact portions thereof. However, the inherent strength of a single one of the known honeycomb elements is comparatively low.

An object of the present invention is to provide a honeycomb element having the features of the preamble of claim 1, which has improved inherent stability. It is desirable that the honeycomb element can be contoured into complicated configurations, such as compound curves consisting of a plurality of continuous curves. Furthermore, it is an object of the invention to provide a honeycomb panel according to the preamble of claim 9, the strength of which is improved by an increased stability of the at least one honeycomb element.

These objects are achieved by the honeycomb element according to claim 1 and by the honeycomb panel according to claim 9.

The honeycomb element according to the invention is characterized by the feature that it is bent in such a way that the abutting side edges of two abutting first surfaces are in contact with each other at least at a portion thereof. This results in the side edges of each connecting wall surrounding a cell being in contact with each other at least at one point, so that the individual cell has an increased resistance to external forces. This increases the inherent stability of the individual honeycomb element.

The prior art honeycomb elements must be laminated and bonded together to form cells. Therefore, to form a honeycomb panel, a plurality of honeycomb elements must be arranged in a specific manner. However, the honeycomb element according to the present invention uses individual rows, each of which can independently resist external forces. Consequently, a plurality of honeycomb elements do not have to be arranged in a specific manner to form a honeycomb core.

The structure and operation of embodiments of the present invention will now be explained.

From the drawings show:

Figures 1A and 1B are views of an intermediate product used to produce a honeycomb element according to the invention;

Figures 2A to 2C are views of a finished honeycomb element bent for use;

Figures 3A and 3B are views of inner and outer radii formed when the honeycomb element is bent;

Figures 4A to 4C are views illustrating the flexibility of the honeycomb element according to the invention;

Figures 5A to 5D are sectional views showing the shape of the cells of further embodiments of the honeycomb intermediate product; Figures 6A to 6C are views of a first embodiment of a honeycomb panel;

Figures 7A to 7B show views of a second embodiment of a honeycomb-shaped panel;

Figure 8 is a view of another application of the honeycomb element;

Figure 9 is a perspective view of a honeycomb element of the prior art;

Figure 10 is a view showing the formation of the curvature in a honeycomb-shaped element of the prior art; and

Figures 11A to 11d show views of a honeycomb-shaped element of the prior art.

Figures 1A and 1B show a honeycomb element in an intermediate stage of the manufacture of the final honeycomb element according to the invention.

As shown in Figures 1A and 1B, each cell 4 in a honeycomb element 5 is formed by a series of first base surfaces 1, a series of top surfaces 2 and connecting walls 3. Each of the first and second surfaces 1, 2 and each of the walls 3 has a rectangular area and creates a cross section in the shape of an equilateral triangle for each cell 4. A connecting angle θ between each first surface 1 and each wall 3 is about 60°. In the honeycomb element 5, each cell 4 is arranged such that the first surfaces 1 are arranged with corners or side edges 1a and 1b between adjacent cells 4 and have a slight clearance, and such that the second surfaces 2 are arranged with corners or side edges 2a and 2b between adjacent cells 4 with a slight clearance.

As shown in Figures 2A and 2B, when the honeycomb element 5 is bent to form a radius of curvature, adjacent side edges 1a and 1b are in contact with each other to form support points 6. The honeycomb element 5 can then be bent in a flexural manner in any direction at the support points 6. The support points 6 therefore ensure stable flexibility of the honeycomb element 5. When the honeycomb element 5 is bent to form a radius of curvature, as shown in Figure 2C, adjacent side edges 1a and 1b are in contact with each other to form support lines 7. These support lines 7 also ensure stable flexibility of the honeycomb element 5. The connection angle ? is so sharp that each bearing point 6 or each bearing line 7 provides adequate and stable flexibility to the honeycomb element 5 even if the first surfaces 1, the second surfaces 2 and walls 3 are thin. When the final products are manufactured, special points P can be soldered.

In the honeycomb member 5 shown in Figs. 1A and 1B, the interval between adjacent side edges 1a and 1b is narrow, and the cell 4 has little clearance therein. The honeycomb member 5 can be bent in such a direction that the adjacent side edges 1a and 1b come into contact with each other. Therefore, the bending direction of the entire honeycomb member 5 is fixed. The honeycomb member 5 can be flexibly bent along the bearing points 6 and bearing lines 7. When the honeycomb member 5 is bent, the first surfaces 1 form an inner bending radius.

As explained above, the honeycomb member 5 can be bent in the manner shown in Figures 2A and 2B. Before the honeycomb member 5 is brazed to a face plate to form a honeycomb panel, the member 5 can also be bent in the following manner.

As shown in Figures 3A and 3B, an outer radius R1 and an inner radius R2 are formed when the honeycomb element 5 is bent. If L is the length of the first surface 1, the bending limit of the honeycomb element 5 can be determined using the following equations:

R1 = (d1/2) + (L²/8d1)

R2 = -(d2/2) + (L²/8d2)

In the above equations, d1 and d2 denote the distances shown in Figures 3A and 3B. Limit distances are used for d1 and d2. These limit distances are required in order to be able to solder the honeycomb element 5 to an end plate. As the above equations show, small radii of curvature can be achieved by adjusting the length L of the first surface 1. In order to further reduce the radius of curvature, both ends of each first surface 1 of the honeycomb element 5 can be trimmed in accordance with the curvature of an end plate in order to minimize the distances d1 and d2.

As shown in Figures 4A and 4B, a honeycomb element can also be twisted about its longitudinal axis. The hatched portion of the strip material for a honeycomb element can be cut out. The strip material is then folded along fold lines a to i to form a honeycomb element as shown in Figure 4C. This honeycomb element can contact a face plate with only a small distance therebetween. Therefore, as long as the fold lines a to i are perpendicular to the length of the honeycomb element 5, the first surfaces 1, the second surfaces 2 and the walls 3 are not restricted to a strictly rectangular shape. By cutting off a portion of the strip material to obtain a suitable curve, a honeycomb element can be easily soldered to a face plate, resulting in the configuration of a honeycomb panel.

As explained above, the honeycomb element according to the present invention can be bent or twisted over various radii of curvature. In a honeycomb core consisting of the honeycomb element, the load-bearing force acts perpendicular to the curved surface of the honeycomb core.

When manufacturing a honeycomb panel, a panel is first pressed into a desired curvature. The honeycomb element of this invention is then placed on a panel, and a face plate is fitted onto the honeycomb element. Through simple manufacturing steps, the honeycomb element can be bent or twisted in the desired manner. Consequently, a honeycomb panel having a complicated set of curvatures can be easily manufactured. Since the sizes of the cells forming the honeycomb element can be easily adjusted, the material thickness, cell heights and curvature of the honeycomb core, as well as other parameters, can be easily adjusted. In this way, a honeycomb core can be or a corresponding panel with the desired strength can be easily manufactured. A honeycomb element can also be produced by folding a strip element along a series of parallel fold lines.

The cells of the intermediate honeycomb element may alternatively have a cross-section in the form of an isosceles triangle or other shape. For example, cells 23 according to Figure 5A may have a circular cross-section and form a honeycomb element 24. As shown in Figure 5B, cells 25 may have a square cross-section and form a honeycomb element 26. As shown in Figure 5C, in a honeycomb element 27, curved first surfaces and second surfaces may also form rows. In a honeycomb element 29 according to Figure 5D, the first surfaces, walls and second surfaces of the cells may have folded reinforcing ribs 28 for strengthening the honeycomb element 29. In the honeycomb elements 24, 26, 27 and 29, the connecting angle Θ between each connecting wall and each first surface of each cell is acute. Therefore, the honeycomb elements 24, 26, 27, and 29 offer the same effects as the honeycomb element 5 consisting of the cells 4.

A first embodiment of a honeycomb panel will now be described in connection with Figures 6A to 6C. In this embodiment, cells 31 having a cross section in the form of an equilateral triangle form a honeycomb element 32 in the same manner as the honeycomb element 5 consisting of the cells 4 explained above and shown in Figures 1A and 1B. The honeycomb element 32 can be used in honeycomb panels having a variety of curvatures. In this embodiment, an aluminum strip material is folded to form the honeycomb element 32 so that three 11 mm long sides form the cells 31. The aluminum strip material has a thickness of 0.2 mm and a width of 13 mm.

As shown in Figure 6B, the honeycomb member 32 is first bent in the same manner as described in connection with Figure 2A so that the inner radius R1 is 50 mm. As shown in Figure 6C, end plates 33 and 34 are then brazed to the inner periphery and outer periphery of the honeycomb member 32 so that a honeycomb panel is formed. The honeycomb member 32 can be flexibly bent and then brazed following the curvature of the end plates 33 and 34. The load-bearing force of the honeycomb member 32 acts perpendicular to the radius of curvature of the end plates 33 and 34, thus achieving adequate strength.

A second embodiment of a honeycomb panel will now be described in connection with Figures 7A and 7B. In this embodiment, the honeycomb element 32 of the first embodiment described above is formed in the same manner as explained in connection with Figure 28. The honeycomb element 32 is then assembled and brazed between the end plates 35 and 36. The end plates 35 and 36 are previously pressed to obtain a compound curve. As shown in Figure 7B, the compound curve consists of a convex curve followed by a concave curve. The convex curve has an inner radius R1 of 70 mm and the concave curve has an inner radius R2 of 45 mm. In this embodiment, the honeycomb element 32 follows the compound curve. Curvature of the honeycomb panel. The honeycomb element 32 is firmly brazed between the end plates 35 and 36. The load-bearing force of the honeycomb element 32 acts perpendicular to the combined radii of curvature, thus providing an adequate strength for the honeycomb panel, for example a compressive strength of about 0.7 kgf/mm².

Another application of the honeycomb elements will now be described in connection with Figure 8. In this embodiment, the honeycomb element 32 is bent in the manner shown in Figure 2C to form a spacer between a honeycomb core 41 and an aluminum block 42 in a honeycomb panel. The honeycomb core 41 consists of known cells having a hexagonal cross-section. A screw thread (not shown) is provided in the aluminum block 42.

A hole 43 is formed in the honeycomb core 41 to receive the aluminum block 42. The honeycomb element 32 is bent and wrapped around the aluminum block 42. The aluminum block 42 is then inserted into the hole 43. The honeycomb element 32 secures the aluminum block 42 in the honeycomb panel and strengthens the section between the aluminum block 42 and the honeycomb core 41. The honeycomb element 32 can thus be used as an individual reinforcement due to its rigidity. At the same time, the honeycomb element 32 can contour any curve of the panel.

Since the honeycomb element 32 fills the section between the aluminum block 42 and the honeycomb core 41, this section has the same strength as the other sections of the honeycomb panel and is more resistant to breakage. The honeycomb element 32 could also be wrapped around the aluminum block 42 in several layers without the layers having to be bonded together.

The present invention has been described above in connection with preferred embodiments shown in the figures. Modifications and changes will occur to those skilled in the art upon reading and understanding the description.

Figures 5A to 5D show cross sections of various configurations that the honeycomb cells have. However, the cross section of the cells is not limited to these configurations. However, the connecting angle between the cell walls and the first surfaces is preferably acute. Since the cross section of the cells is not limited to an equilateral triangle, the cells may have an opening therein. Furthermore, the material of the honeycomb element is not limited to the specified material.

Claims (9)

1. Honeycomb element for a honeycomb core or a honeycomb panel, which is elongated and comprises a plurality of rectangular first surfaces (1) arranged one behind the other and extending in the axial direction of the element (5, 24, 26, 27, 29, 32) and further connecting walls (2, 3) each of which runs substantially perpendicular to the length of the element (5, 24, 26, 27, 29, 32) and is connected to adjacent side edges (1a, 1b) and two adjacent ones of the first surfaces (1), wherein the connecting walls (1, 2) define a plurality of axially spaced cells (4, 23, 25, 31), characterized in that the element (5, 24, 26, 27, 29, 32) is bent in such a way is that the adjacent side edges (la, 1b) of the two adjacent first surfaces (1) are in contact with each other at least in one section (6, 7) thereof. 2. Honeycomb element according to claim 1, wherein the space between the connecting walls (2, 3) and the axially connecting angle formed by the spaced first surfaces (1) is less than 90º. 3. Honeycomb element according to claim 2, wherein the connection angle is about 60°. 4. Honeycomb element according to claim 1, wherein the adjacent side edges (1a, 1b) are in contact with each other along a line (7) to form a continuous load-bearing surface perpendicular to a radius of curvature with which the element (5, 24, 26, 27, 29, 32) is bent. 5. Honeycomb element according to claim 1, in which the cells (4) have a substantially triangular cross-section. 6. Honeycomb element according to claim 1, wherein the cells (25) have a substantially rectangular cross-section. 7. Honeycomb element according to claim 1, wherein the cells (23) have a substantially circular cross-section. 8. Honeycomb element according to claim 1, in which the element (5, 24, 26, 27, 29, 32) consists of aluminum. 9. Honeycomb panel with two end plates (33, 34, 35, 36) and at least one honeycomb element (5, 24, 26, 27, 29, 32) which is arranged between the two end plates and fastened thereto, characterized in that the at least one honeycomb Element (5, 24, 26, 27, 29, 32) is arranged in the manner defined in any one of claims 1 to 8.